Bleaching cyanoethylated cotton fibers with hydrogen peroxidephosphate solution and optionally with water-soluble sulfoxylate solution



United States Patent 2,860,945 iiLnAoHmG CYANGETHYLATED COTTON FIBERSWITH HYDRDGEN PEROXIDE- PHOSPHATE SOLUTION AND OPTION- ALLY WITHWATER-SOLUBLE suLFoX- YLATE soLUTro Robert B.D ustman, Jr., NiagaraFalls, N. Y., assignor to E. I. du Pont de Nemours and Company,Wilmington, DeL, a corporation of Delaware No Drawing. Application July28, 1955 Serial No. 525,064

10 Claims. (Cl. 8-110) This invention relates to the bleaching ofcyanoethylated cotton fibers and fabrics.

Cyanoethylated cotton is a relatively new type of fiber obtained byreacting cotton with acrylonitrile under alkaline conditions. The extentof cyanoethylation obtained varies with the conditions employed incarrying out the reaction. Fabrics containing cyanoethyl groupscorresponding to from about 1.8 to 6.5% nitrogen have been reported.Presence of the cyanoethyl groups makes the modified cotton fiberresistant to micro-organism attack, more resistant than cotton to wetand dry heat degradation, more receptive to dyes, and more resistant toabrasion. (Parks, American Dyestutf Reporter, November 22, 1954, pages774-779.) Although characterized by these desirable properties,whichappear to be directly related to the presence of the cyanoethyl groups,these fibers have the distinct disadvantage of being difiicult to bleachwithout causing serious reduction in their nitrogen content andconsequent destruction of the desirable properties.

It is an object of the invention to provide an improved method forbleaching cyanoethylated cotton fibers and fabrics. A further object isto provide a method whereby such fibers can be successfully bleachedwithout substantial reduction in their nitrogen content. Other objectswill be apparent from the following description.

' The objects of the invention are accomplished by subjectingcyanoethylatedcotton'fibers to the action of an aqueous alkalinesolution of hydrogen peroxide whose alkalinity is due essentially to thepresence of a molecularly dehydrated phosphate. In one embodiment of theinvention, the fibers are also subjected to the action of an aqueoussolution of a soluble formaldehyde sulfoxylate, preferably preceding thetreatment with the peroxide solution.

It has now been found that cyanoethylatedcotton fibers can beeffectively bleached by the action of a hydrogen peroxide solution madealkaline by the presence of a molecularly dehydrated water-solublephosphate without any significant reduction in the nitrogen content ofthefibers resulting. The action of such a peroxide solution is ratherunique in that peroxide solutions alkalized by means of caustic soda,sodium silicate or borax,a11 commonly employed in alkaline peroxidebleach formulas, cause excessive reduction of the nitrogen content ofthe fibers with consequent degradation of their desirable properties. 1

Greater fiber brightnesses than those obtainable by e a peroxidetreatment alone 'can be achieved by subjecting I the fibers to aseparate treatment with an aqueous solution of "a soluble formaldehydesulfoxylate. This separate treatment mayfollow or precede the peroxidetreatment. If used, it is usually preferable that it precede theperoxide treatment. It hasbeen found that such .a treatment with aformaldehyde sulfoxylate is about twice as effective in increasing thebrightness of the fibers as is sodium hydrosulfite, one of the most com-H 2,350,945 Patented Nov. 18, 1958 mon bleaching agents of the reducingtype. Furthermore, it bleaches without causing any significant reductionin the nitrogen content of the fibers.

The invention is illustrated by the following examples 5 in which allpercentages are percentages by weight.

EXAMPLE 1 Samples of a sized greige cyanoethylated cotton fabric weretreated with peroxide baths of various compositions to determine thebleaching effectiveness of-the baths and their effect upon the nitrogencontent of the fabric. The treatments involved immersing the simple inthe bath for 1 hour at 180 F. (except as noted for Bath A) at a 40:1weight ratio of liquor to fabric. The compositions of the bathsevaluated are shown below. The treated samples were washed in water,air-dried and ironed, and their brightnesses reflectances) determined,using a Hunter multipurpose refiectometer. The nitrogen contents of thetreated samples were de- 20 termined by the Kjeldahal method. Theresults obtained are shown in the table.

. Bath A 0.5% hydrogen peroxide (H 0 0.24% borax 0.24% of an alkyl arylpolyether alcohol, a wetting agent Bleaching was for 15 minutes at 195"F.

Bath B 0.3% hydrogen peroxide (H 0 0.6% 42 B. sodium silicate(containing the equivalent of about Na O, 25% Si0 and 65% water) Bath C0.3% hydrogen peroxide (H 0 0.24% tetrasodium pyrophosphate (Na4P2o7)Bath 0.3% hydrogen peroxide (H 0 0.24% of an alkyl aryl polyetheralcohol, a wetting agent Bath E 0.3% hydrogen peroxide (H 0 0.35% borax0.24% magnesium sulfate (MgSO -7H O) 0.3% hydrogen peroxide (H 0 0.6% 42B. sodium silicate 0.36% borax 0.12% magnesium sulfate (MgSO -7H O) Itwillbe noted from the table that of the 6 baths evaluated, only Bath Cgave a final brightness (percent reflectanceyabove 57 without causingexcessive reduction in the nitrogen content of the fabric.

' EXAMPLE 2 A sample of the greige fabric of the above example wassubjected to a two-stage treatment. A. 1% solunon of normal zincformaldehyde sulfoxylate was employed at a liquor to fabric. ratio of20:1 for 1 hour at compounds of this class.

v terials are preferred. 1

' after the second stage was 69.5%, while the final nitrogen content ofthe treated fabric was 3.18%, the same as for the untreated fabric.

The use of sodium formaldehyde sulfoxylate in place of the zinc compoundproduces similar results.

EXAMPLE 3 A sample of the sized, greige cyanoethylated cotton fabric ofthe above examples was immersed 0.5 hour at 180F. in a 1% solution ofnormal Zinc formaldehyde sulfoxylate at a liquor to fabric ratio of40:1. The sample was rinsed in water then bleached employing a solutioncontaining 0.6% hydrogen peroxide (H and 0.24% sodium tripolyphosphate(Na P O Bleaching was continued for 1 hour at 180 F. at a liquor tocloth ratio of 40.21. The reflectance of the bleached sample was 71.0%and its nitrogen content was 3.12% compared with values of about 34.2%and 3.18%, respectively, for the untreated fabric.

EXAMPLE 4 A sample of the sized, greige, cyanoethylated cotton fabric ofthe above examples was bleached for 1 hour drying, its reflectance was74.7% as compared with an original value of about 34.2%.

V EXAMPLE 5 A sample of the above sized, greige, cyanoethylated cottonfabric was bleached 2 hours at 180 F. at a 40:1 liquor to fabric ratioemploying a bath containing 0.6% hydrogen peroxide (H 0 and 0.24% sodiumtripolyphosphate. The sample was then rinsed in Water and dried. Thereflectance was 72.0%. The sample was next immersed in a 1% solution ofnormal zinc formaldehyde sulfoxylate for -1 hour at 180 F. at a 40:1liquor. to fabric ratio. The sample was rinsed with water and dried andits reflectance was found to be 75.9% as compared with an original valueof about 34.2%.

The ,agent employed for rendering alkaline the peroxide treatingsolution can be any water-soluble molecularly dehydrated phosphate, suchas the alkali metal Examples are the sodium pyrophosphates, sodium.tripolyphosphate and hexametaphosphate. Minor amounts of otherconventional alkaline materials may'l-be present 'but the alkalinityofthe treating solution should be ;due essentially to a molecularlydehydrated phosphate, otherwise substantial decrease in the nitrogencontent of thejfiber results. .Solutionsentirely free of such otheralkaline ma- The sulfoxylate treating solution may contain as the activeagent any water-soluble formaldehyde sulfoxylate,

sodium examples of which are sodium formaldehyde sulfoxylate, 1

normal zinc formaldehyde sulfoxylate and basic zinc formaldehydesulfoxylate, iv

The sulfoxylate and peroxide treatments may be applied in any desiredsequence, although it is usually preferred that the peroxidetreatmentfollow the sulfoxylate treatment...The treatments may be applied tofabric without first desizing. the fabric, as illustrated in theforegoing examples. However, the fabric can be first, desized and thentreated -in--accordance with the inven-fi tion, in which case, adesizing treatment should be em-.; ployed which will effectively desizewithout reducing the nitrogen content of the fabric. A 2% Rapidaseenzyme solution applied for 1 hour at 180 F. at a liquor L to fabricratio of 20:1 is suitable for that purpose; Rapidase, a textile desizingproduct of the Wa1lerstein Company, is a'liquid enzyme preparationcontaining liquefying and proteolytic enzymes. a

- The concentration of soluble formaldehyde sulfoxy late in thesulfoxyla'te treating solution, if usedj, ma y be varied considerablydepending upon the results de sired. Concentrations of from about 0.5 to5% are gen erally suitable, concentrations of from 1 to 3% being"usually preferred. Such solutions can be used at any desired liquor tofabric ratio, e. g. from 40:1 to 1:1. Temperatures from room temperatureto the boiling tem- 1 perature are suitable, the lower temperaturesrequiring longer times than the higher temperatures. Preferredtemperatures range from about to 212 F. g The concentration of hydrogenperoxide (H 0 in. the peroxide treating liquor will depend upon theamount; of bleaching desired. Generally it will range from" about 0.1 to2% or higher,'concentrations ranging from about 0.2 to about 1% (as H 0being generally pref ferred. The content of molecularly dehydrated phosphate in the peroxide solution usually should be atleast about 0.1% andmay be as high as about 4% orsorne-= what higher, the preferred rangebeing 0.5 to 3%.; conditions as regards temperature and liquor to fabricratio indicated for the sulfoxylate treatment also apply. to theperoxide treatment. a 1

The method of the invention providesa way of increasing the brightnessof cyanoethylated cotton fibers and fabrics without causing excessivereduction intheir nitrogen contents. It, therefore, makes possiblebleaching such materials without destroying or reducing those desirableproperties of this type of fabric'which are due to thepresence'ofcyanoethyl substituent groups in the fiber. I

Iclaim: I 1. The method of bleaching, cyanoethylated cotton fiberscontaining cyanoethyl groups equivalent to from 1.8 to 6.5% nitrogenbased upon the weight of said fibers comprising bleaching said fiberswith an aqueous; alkaline solution of hydrogen peroxide in which thealkaline agent consists essentially of a water solnblealkalimetalmolecularly dehydrated phosphate, at a tempera ture in the range fromroom temperature to the boiling temperature of said solution, saidsolution containing from 0.1 to'2% -H O and from 0.1 to 4% of said phosephate. qr j 2. The method of claim 1 carried out at a temperature withinthe range 160 to 212 F. 3. The method of claim 2' wherein bleaching is efected while the fibers are immersed in} the hydroge peroxide solution-.7 i a 4. The method of bleaching cyanoethylatedcotto fibers containingcyanoethyl groups equivalent to from 1.8 to6.5% nitrogen based upon theweight ofsaid fibers comprising bleaching saidfibers, in twoseparatebleaeh ing 'treatments;With solutions; (1 and (2) .at .a temperature in each treatment; between roorn temperature'and. the boilingtemperature of the solution used,.said solu. tion (-1) being an aqueousalkaline"-hydrogen peroxide, solution in which the alkaline agentconsists essentially of a water-soluble alkalimetal molecularlydehydrated phosphate which ;is present at a concentration of from' 0.1to 4% along with from 0.1 10 2% I -1 9 and said: solution (2;) being a0.5 to 5% aqueousgsolu tion of?- water-soluble 'sulfoxylate" from thegroup consisting of the sodium .and'zinc formaldehydesulfoxylates.' L H5. The'method of'claim-= 4 wherein the treatmentswith solution (-1)precedes the treatmentwith solutiont2). f

6. The method of claim 4 wherein the treatment with solution (1) followsthe treatment with solution (2).

7. The method of claim 4 wherein both treatments are carried out at atemperature within the range 160 to 212 F.

8. The method of claim 7 wherein the treatment with each solution iseffected by immersing the fabric in the appropriate solution.

9. The method of claim 1 employing sodium pyrophosphate.

10. The method of claim 1 employing sodium tripolyphosphate.

6 References Cited in the file of this patent UNITED STATES PATENTSKaufiman Feb. 11, 1941 McEwen June 6, 1950 OTHER REFERENCES ChemicalAbstrs. (1), 1940, 34, p. 8294 ,-abstract of I. Proc. Sydney Tech. Coll.Chem. Soc. 7, 61-64 (1935- 37).

Chem. Abstrs. (2), 1944, 38, p. 2215, abstract of Teintex 1941, 6, pp.222-226.

Textile Colorist, pp. 407-411, September 1943.

4. THE METHOD OF BLEACHING CYNAOETHYLATED COTTON FIBERS CONTAININGCYUANOETHYL GROUPS EQUIVALENT TO FROM 1.8 TO 6.5% NITROGEN BASED UPONTHE WEIGHT OF SAID FIBERS COMPRISING BLEACHING SAID FIBERS IN TWOSEPARATE BLEACHING TREATMENTS WITH SOLUTIONS (1) AND (2) AT ATEMPERATURE IN EACH TREATMENT BETWEEN ROOM TEMPERATURE AND THE BOILINGTEMPERATURE OF THE SOLUTION USED, SAID SOLUTION (1) BEING AN AQUEOUSALKALINE HYDROGEN PEROXIDE SOLUTION IN WHICH THE ALKALINE AGENT CONSISTSESSENTIALLY OF A WATER-SOLUBLE ALKALI METAL MOLECULARLY DEHYDRATEDPHOSPHATE WHICH IS PRESENT AT A CONCENTRATION OF FROM 0.1 TO 4% ALONGWITH FROM 0.1 TO 2% H2O2, AND SAID SOLUTION (2) BEING A 0.5% AQUEOUSSOLUTION OF A WATER-SOLUBLE SULFOXYLATE FROM THE GROUP CONSISTING OF THESODIUM AND ZINC FORMALDEHYDE SULFOXYLATES.